I have a stock 2002 Focus hatchback with 170,000 miles. It's throwing a p0456 code but has no other issues -- it runs fine at idle and on the road, and it has no loss in fuel economy. I have replaced the gas cap, but the light is still on.

Usually this P0456 code is caused by an incorrect or faulty gas cap. Filling the fuel tank with the engine running could conceivable cause this code as well or if the cap wasn't properly tightened. Any of the following could also be the cause:

* A small leak in any of the EVAP hoses or fuel tank hoses
* A small leak in the purge valve or vent valve
* The EVAP Canister may be leaking

The EVAP charcoal canister is at the rear of the fuel tank. Sorry, no pics. You need to get underneath to have a look. Check the hoses aren't loose or perished.

The purge valve is in the engine compartment, passenger side (arrowed). It has a small vacuum line going from it to the intake manifold (#1) and a second larger line (#2,#3 - arrow at each end) going from the valve to the manifold, as well. There's an electrical connector on top. Check none of the lines exiting from it are damaged, crimped or loose. Most importantly, check the U-shaped line going into it. (Not marked in pic.) The system is supposed to be "air-tight". Lines sometimes get damaged when work is being done on some engine component close by.

A "smoke test" is usually used to find leaks from what I'm told.

The purge valve may have also failed or be stuck but that would probably throw a different code P0455.

IMO, it's more likely the leak is at the fuel tank end but a quick check of the engine compartment pieces wouldn't hurt.

I have had this error recurring in my '06 ZXW for about a year. It has 96K miles. The Ford dealer has had the car 5 or 6 times to try to fix the problem. The latest go round seemed to fix it. But yesterday the vehicle just shutdown at a store leaving me stranded. I was able to jump start the vehicle and get it home, but the car still wouldn't turn over. I plugged my CANOBD2 into the vehicle and got this same error message again. If this is the same error as before, then clearly there is a manufacturing defect with this vehicle. Judging by the numerous other posts, I am not alone, Ford has even issued Tech Bull. on it. I wish Ford would step up and fix the problem once and for all. The dealer is at a loss, and I think they are trying to do a work around on the electronics at this point. Anyone else in this boat?

I doubt that is what's causing your car not to crank. I assume you said it was the same problem because you used a code scanner and came up with the same code? If not, then how can you be sure that it's the same problem? If a car doesn't start with anything but a jump- then that's usually a sign of a bad battery. This can happen at any time, and your problem: getting the car back from the dealer and having it die a week later, is what I'd call an evil coincidence. That happens more often than you think. A car goes in for a repair, and a few days later something else breaks that is completely unrelated to the repair, or even the same area the repair is in. This leads conspiracy theorists like Jello Biafra to write songs like "Trust Your Mechanic" when it's really an act of nature.

Thanks for your feedback. Initially I thought it was the battery too, but there is usually some warning before the battery goes. I had driven the car for 45 mins. at about 45 mph, got out of the car at a store and it was stone dead when I came out 5 mins later. So it could be, but I thought I would check the OBD code to see if it would say anything else and I got the PO456, again. The dealer had last fixed that issue for the 5th/6th time about 3 months ago. I will check the battery too.

The EVAP charcoal canister is at the rear of the fuel tank. Sorry, no pics. You need to get underneath to have a look. Check the hoses aren't loose or perished.

The purge valve is in the engine compartment, passenger side (arrowed). It has a small vacuum line going from it to the intake manifold (#1) and a second larger line (#2,#3 - arrow at each end) going from the valve to the manifold, as well. There's an electrical connector on top. Check none of the lines exiting from it are damaged, crimped or loose. Most importantly, check the U-shaped line going into it. (Not marked in pic.) The system is supposed to be "air-tight". Lines sometimes get damaged when work is being done on some engine component close by.

A "smoke test" is usually used to find leaks from what I'm told.

The purge valve may have also failed or be stuck but that would probably throw a different code P0455.

IMO, it's more likely the leak is at the fuel tank end but a quick check of the engine compartment pieces wouldn't hurt.

Excellent write up the Focus Evap system. My wife wagon engine light came on and I took it to nearby auto zone thinking o2 sensor was bad. Car has 48k for 03 model. We had that issue with P456 5 years ago and we replaced the cap. Now it's back again. Your write up gave me more information to the point. Keep up the good work.

My car (2002, 125,000 miles) was showing this code a several months ago. (I didn't get a CEL, but I have an Ultragauge and it came up as a pending code). I tightened the gas cap a few clicks and it stopped a few days later. Then it came back and I again tightened the cap and it did not go away. This time, I took the cap off and noticed a lot of grime and dirt on the filler neck where it meets the cap. Wiped that and the sealing O-ring on the cap off with a paper towel, and put the original cap back on and so far I haven't seen the code again.

UPDATE: The above turned out to be short-lived. I'm getting the pending code again, but it doesn't happen consistently, so it's a pain to track down - I'll probably replace the fuel cap first.

UPDATE: 31Mar2013 - New fuel cap fixed it for me ... so far, at least!!!

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